[clang] [Clang][P1061] Fix template arguments in local classes (PR #121225)

[Jason Rice via cfe-commits]

ricejasonf wrote:

I verified that it is still broken on trunk (on godbolt). It is now rebased on `main` with a shiny new release note. Please merge it if you think it is the right fix (and the tests finish). @cor3ntin 

https://github.com/llvm/llvm-project/pull/121225